RHEOLOGICAL PROPERTIES OF CARBOPOL-BASED GELS

Carbopol (crosslinked polyacrylic acid) microgels are ubiquitous high‐viscosity thickeners and model yield-stress fluids in pharmaceutical, cosmetic, biomedical, and industrial applications[3]. Their rheological behavior arises from an ionizable, crosslinked network that swells upon neutralization to form a solid-like gel (with storage modulus G′ greatly exceeding loss modulus G″ in the linear regime)[3][6]. In this review we synthesize recent advances (2020–2025) in Carbopol gel rheology, highlighting experimental methodologies and fundamental mechanisms. We discuss how small-amplitude oscillatory shear (SAOS) yields nearly frequency-independent elasticity (constant G′) at low strain[6], while yielding in large-amplitude oscillatory shear (LAOS) creates a crossover to viscous flow at a critical strain. Steady shear tests typically show Herschel–Bulkley flow (τ = τ_y + k·γ̇ⁿ) with pronounced shear-thinning and measurable yield stress, which increases with polymer concentration and varies with pH[6] studies emphasize Carbopol’s thixotropic “avalanche” behavior just above τ_y[5] and advanced rheometry (e.g. cavitation rheology) to probe its yield and interfacial properties[4].